It is said that Abp. Lefebvre once commented to a seminarian in 1977 that this was the best book on the New Mass. That is quite believable given the excellence of this book. The author's research is deep, his arguments are compelling, and his judgments are reasoned and measured.
The work tackles three difficult questions head-on (not sure why the book was given the unfortunate title of "Two Timely Issues"):
1. Whether the New Mass is good or bad -- De Silveira's devastating presentation of the problems with the New Mass was so feared by Pope Paul VI that he forbade the publication of the work, seven years after he had abolished the Index. This is one of the reasons why this book is so little known in the English speaking world. The book is worth the purchase for this section alone.
2. Whether it is possible for a Pope to promulgate a liturgy that is dangerous to the faith -- De Silveira points out that, while theologians have traditionally held that disciplinary laws are infallible, they have yet always qualified their opinion with limiting clauses. As such, circumstances can indicate that they are not so. In the case of the New Mass, it was clear that Pope Paul VI did not want to engage the charism of infallibility by the fact that he stated: "the rite and the respective rubrics are not by themselves a dogmatic definition; they are susceptible of theological qualification of varying value, according to the liturgical context to which they refer".
3. Whether a Pope can be heretical and, if so, whether he falls automatically from his office -- This has to be the clearest presentation of this topic that I have seen to date. De Silveira takes St. Robert Bellarmine's treatment of the question and identifies five different possible opinions on the question. Then, he considers which opinions theologians in the history of the Church have chosen as their own on the question. De Silveira himself leans towards the fifth opinion, that a heretical Pope automatically loses office once his heresy becomes manifest. This does not mean that De Silveira is a sedevacantist. On the contrary, as he clarifies on p. 230, the heresy is not manifest as long as the vast body of the Church continues to accept the Pope. There needs to be some procedure against the Pope by which he is rebuked for his heresy and he persists in it for the heresy to be manifest.
In short, this book is gold and I highly recommend it for the thoughtful reader trying to make sense of a very confusing time in the Church.